A flat panel display possesses advantages of being ultra thin, power saved and radiation free and has been widely utilized. Present flat panel displays mainly comprise a LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Display).
To be compared with a well developed TFT-LCD, an OLED based on the Organic Light Emitting Diodes is an active light emitting display, which possesses outstanding properties of self-illumination, high contrast, wide view angle (up to 170°), fast response, high luminous efficiency, low operation voltage (3-10V), ultra-thin (thickness smaller than 2 mm) and etc. The display devices utilizing OLED technology has possibility to have a lighter, thinner, charming appearance, more excellent color display quality, wider view range and greater design flexibility.
Thin Film transistors (TFT) are important components of a flat panel display which can be formed on a glass substrate or a plastic substrate. Generally, the tin film transistors are employed as light switching-on elements and driving elements utilized such as LCDs, OLEDs, Electrophoresis Displays (EPD).
The oxide semiconductor TFT technology is the most popular skill at present. Because the carrier mobility of the oxide semiconductor is 20-30 times of the amorphous silicon semiconductor. With the higher electron mobility, it is capable of magnificently raising the charging/discharging rate of TFT to the pixel electrodes to promote the response speed of the pixels and to realize faster refreshing rate. In the mean time, the line scan rate of the pixels also can be promoted to make the manufacture of the flat panel display having ultra high resolution become possible. In comparison with the Low Temperature Poly-silicon (LTPS), the oxide semiconductor manufacture process is simpler and possesses higher compatibility with the amorphous silicon process. It can be applicable to the skill fields of Liquid Crystal Display, Organic Light Emitting Display, Flexible Display and etc. Because it fits the new generation production lines and has possible applications for displays with Large, Middle and Small sizes. The oxide semiconductor has the great opportunity of application development.
In a present oxide semiconductor TFT substrate structure, the oxide semiconductor layer generally directly contacts the source/the drain in general and electrical connections are formed therebetween. However, the ohm contact resistance between the oxide semiconductor layer and the source/the drain, the ohm contact resistance between the pixel electrode layer and the source/the drain are larger and leads to higher driving voltage, higher power consumption and lower response speed of the flat panel display.
The power saving is real a required topic to the development of the present society. Making great efforts to develop low power consumption flat panel display becomes an important target to all flat panel display manufacturers.